The following disclosure relates to bonding on a substrate, such as a silicon die. In some implementations of a fluid ejection device, fluid droplets are ejected from one or more nozzles onto a medium. The nozzles are fluidically connected to a fluid path that includes a fluid pumping chamber. The fluid pumping chamber is actuated by a transducer, and when actuated, the fluid pumping chamber causes ejection of a fluid droplet. The medium can be moved relative to the fluid ejection device. The ejection of a fluid droplet from a particular nozzle is timed with the movement of the medium to place a fluid droplet at a desired location on the medium. In these fluid ejection devices, it is usually desirable to eject fluid droplets of uniform size and speed and in the same direction in order to provide uniform deposition of fluid droplets on the medium.